Weather and Climate Extremes in a Changing Climate. Regions of ...

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The NOAA Science Advisory Board established
an expert Hurricane Intensity Research
Working Group that recommended
specific action on hurricane intensity and
rainfall prediction (NOAA SAB, 2006);
The American Geophysical Union convened
a meeting of scientific experts to
produce a white paper recommending
action across all science-engineering and
community levels (AGU, 2006); and
A group of leading hurricane experts convened
several workshops to develop priorities
and strategies for addressing the most
critical hurricane issues (HiFi, 2006).
While much of the focus for these groups was
on the short-range forecasting and impacts
reduction aspects of hurricanes, the research
recommendations also apply to longer term
projections. Understanding the manner in
which hurricanes respond to their immediate
atmospheric and oceanic environment would
improve prediction on all scales.
An issue common to all of these expert findings
is the need for understanding and parameterization
of the complex interactions occurring at the
high-wind oceanic interface and for very high
model resolution in order for forecast models
to be able to capture the peak intensity and
fluctuations in intensity of major hurricanes.
Climate models are arriving at the capacity to
resolve regional structures but not relevant details
of the hurricane core region. As such, some
form of statistical inference will be required to
fully assess future intensity projections.
4.7
Establishing a globally-consistent
wind definition for determining
hurricane intensity would allow
for more consistent comparisons
across the globe.
A major issue with determining the intensity
of hurricanes lies with the definition of wind
speed. The United States uses a one-minute average
and the rest of the world uses ten minutes,
which causes public confusion. For example, a
hurricane could be reported using one-minute
Weather and Climate Extremes in a Changing Climate
Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands
winds while it was still a tropical storm by a tenminute
standard. This is becoming more serious
with the spread of global news in which a U.S.
television channel can be reporting a hurricane
while the local news service is not. A related
issue lies with comparing aircraft and numerical
model “winds” with those recorded by
anemometers: an aircraft is moving through the
atmosphere and reports an inherently different
wind; the wind speed in a model is dependent
on the grid spacing and time step used.
4.8
Improvements in the ability
of climate models to recreate
the recent past as well as make
projections under a variety of
forcing scenarios are dependent
on access to both computational
and human resources.
The continued development and improvement
of numerical climate models, and observational
networks for that matter, is highly related to
funding levels of these activities. A key factor
is the recruitment and retention of people
necessary to perform the analysis of models
and observations. For the development and
analysis of models, scientists are drawn to institutions
with supercomputing resources. For
example, the high resolution global simulations
of Oouchi et al. (2006) to predict future hurricane
activity are currently beyond the reach of
U.S. tropical cyclone research scientists. This
limitation is also true for other smaller-scale
storm systems, such as severe thunderstorms
and tornadoes. Yet, to understand how these
extreme events might change in the future it is
critical that climate models are developed that
can realistically resolve these types of weather
systems. Given sufficient computing resources,
current U.S. climate models can achieve very
high horizontal resolution. Current generation
high performance computing (HPC) platforms
are also sufficient, provided that enough access
to computational cycles is made available.
Furthermore, many other aspects of the climate
system relevant to extreme events, such as
extra-tropical cyclones, would be much better
simulated in such integrations than they
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